Just because the tutorial talks about tabs doesn't mean you need to use different methods for other elements. If it helps, mentally change "tab" to "heading".

You will need another wrapper div to hold the second bg image. In /includes/modules/your_template/new_products.php, find this near the bottom:
PHP Code:
    if (isset($new_products_category_id) && $new_products_category_id != 0) {
      
$category_title zen_get_categories_name((int)$new_products_category_id);
      
$title '<h2 class="centerBoxHeading">' sprintf(TABLE_HEADING_NEW_PRODUCTSstrftime('%B')) . ($category_title != '' ' - ' $category_title '' ) . '</h2>';
    } else {
      
$title '<h2 class="centerBoxHeading">' sprintf(TABLE_HEADING_NEW_PRODUCTSstrftime('%B')) . '</h2>';
    } 
and change to
PHP Code:
    if (isset($new_products_category_id) && $new_products_category_id != 0) {
      
$category_title zen_get_categories_name((int)$new_products_category_id);
      
$title '<h2 class="centerBoxHeading"><span class="centerBoxHeadingWrapper">' sprintf(TABLE_HEADING_NEW_PRODUCTSstrftime('%B')) . ($category_title != '' ' - ' $category_title '' ) . '</span></h2>';
    } else {
      
$title '<h2 class="centerBoxHeading"><span class="centerBoxHeadingWrapper">' sprintf(TABLE_HEADING_NEW_PRODUCTSstrftime('%B')) . '</span></h2>';
    } 
Then you can attach one side of the bg to h2.centerBoxHeading and the other side to .centerBoxHeadingWrapper.